Non-toxic gas generation

ABSTRACT

THERE ARE DISCLOSED COMPOSITIONS OF SOLID MATERIALS CAPABLE OF PRODUCING NON-TOXIC GASES BY A RAPID CHEMICAL REACTION UPON INITIATION OF THE REACTION. THE SOLID MATERIALS COMPRISE A SOLID INORGANIC REDUCING AGENT AND A SOLID INORGANIC OXIDIZING AGENT MIXED TOGETHER IN FINELY DIVIDED OR GRANULAR FORM AND COMPACTED WITHOUT THE PRESENCE OF EITHER A BINDER OR SOLVENT. TYPICAL SOLID INORGANIC REDUCING AGENTS ARE THE SALTS OF HYDRAZINE, HYDROSYLAMINE AND HYDRAZOIC ACID. TYPICAL SOLID OXIDIZING COMPOUNDS ARE THE SALTS OF NITRIC ACID, NITROUS ACID, CHLORIC ACID AND PERCHLORIC ACID. THE GASES TYPICALLY PRODUCED ARE SOME OR ALL OF NITROGEN, WATER AND OXYGEN, AND WITHOUT THE PRESENCE OF TOXIC GASES SUCH AS THOSE CONTAINING CARBON. THE GASES ARE DEVELOPED SPONTANEOUSLY WITHIN MILLISECONDS BUT WITHOUT EXPLOSIVE FORCE.

United States Patent 3,814,694 'NON-TOXICGAS GENERATION Karl Klager, Sacramento, and Albert 0. Dekker, Carmichael, Califl, assignors to Aerojet-General Corporation, El Monte, Calif.

No Drawing. Filed Aug. 9,,1971, Ser. No. 170,325 Int. Cl. B60r 21/08,.(30611 /06; (109k 3/00 U.S..Cl. 252-186 p 28 Claims ABSTRACT OF -THE DISCLOSURE There are disclosed compositions of solid materials capable of producing non-toxic gases by. a rapid chemical reaction upon initiation of the reaction. The solid materials comprise 'as'solid inorganic reducing agent and a solid inorganic oxidizing agent mixed together in finely divided" or granular forrn and'cornpacted without the presence ofeither .a binder or solvent. Typical solid inorganic reduc'firig a'gen't's" are the salts of hydrazine, hydroxylamine and hydrazoic acid.,'l'ypical solid oxidizing compoundsare. the salts of nitric acid, nitrous acid, chloric acid and perchloric acid. The gases typically produced aresome or .all of, nitrogen, Water and oxygen, and Without the presence of toxic gases such as those containing carbon."Thegases are developed spontaneously within milliseconds butwithout explosive force.

This invention relatesvto "gas generation and particularly to generation of non-toxic gases.

An obj'ect is to generate 'gases which are non-injurious to humans or animals.

=*There"are circumstances iunderai'which it can be desirable'to generate non-.toxic..gases' such as those normally present -:in-th e air", .forexample'inspace craft, submarines, underground mines and"other'enclosed places. An important use. of such.1g' eneratedj .gas, is in the filling of air bags such as those used and proposed'zfor use in vehicles. foripassengerzsafetyipurposes; r Zinnia" A Gas generation andgas generators havelong beenwellj known. It has, for example, been well-known to use propellant compositions for gas generation such as for creating jets for drivingaircr aft and .missiles or for driving other mechanisms. The compositions ordinarily used for such" purposes have'comprised an oxidizer and a binder within which thel oxidizer isdispersed, and in such compositions there has been combustion of the binder matean ordinarily containingfcarbonaceous matter, and this has generated toxic'or vdar'igerous fend products such as carbon -monoxide and carbon dioxide, as well as water which isfnonrtoxicother gas generator propellants heretofore iin use'have been based onnitrocellulose both as a singlebasefpropellant and also in combination with nitroglycerin as, ajdouble base propellant, which carries the.

oxidizer in anintra-molecular.form. The gas generation from thehitrocellulose basesubstances, also occurs in acombustion process. Since the nitrocellulose base propella ntslikewisecontain carbon, there are developed the sa me lginds of. carbonaceous end products," toxic or dank gerou sinsofar as constituting Lari, environment for human. life isg'concerned. i l i viously'canno't be used safely in an atmosphere intended for sustaining human life..In. the case of .airbagsg 'these'j have been used. andv proposed .for. protecting occupants? presenceof'the inflat'e'd'air bag l- Such bags are required In accordance with the present invention, there are provided compositions of solid materials without either binder or solvent, capable of producing gases in a rapid chemical reaction free from undesirable toxic carbonaceous gases.

The compositions according to the present invention produce nitrogen, water and oxygen as typical non-toxic gases, such as are also found in the air, and they supply the gas spontaneously within milliseconds after initiation of the reaction, and without explosive force. Such gases therefore fulfill the requirement of toxic-free gases such as can be safely used in air bags and other confined places where human or animal life is to be sustained.

It is not always essential that every one of these nontoxic gases be found in the product of a generator for the non-toxic gases. For example, under some circumstances, the generated gas need not have oxygen, and this can be a safe condition under those circumstances where the generated gas is to be injected into an atmosphere which already contains suflicient oxygen.

We carry out our present invention by use of a binderless mixture of solid inorganic oxidizer material and solid inorganic reducing agent, capable of entering into an exothermal chemical reaction, producing toxic-free and safe gases. Typical solid inorganic reducing agents useable for this purpose are the salts of hydrazine, hydroxylamine, and hydrazoic acid. Typical solid oxidizing compounds useable for the purpose are the salts of nitric acid, nitrous acid, chloric acid and perchloric acid. One or more of the inorganic reducing agents is mixed with one or more of the inorganic oxidizing agents, and for this purpose, the materials can be ground and blended to a proper particle size which permits compaction ofthe mixture with a minimum of voids.

The reactants are preferably pulverized to the smallest particle size possible, dried to be free of moisture and then mixed in an inert humidity-free atmosphere. This integrated mixture then is pressed into amold. Suitable presses are a Carver press or a pill press that compress ,1 a hot electric wire, or a typical prime initiator such as commonly usedin explosive devices, or by a hammer ball as in a pistol or any shock similar tothat commonly required for the ignition of explosive charges.;0nce the reaction is thus initiated, the exotherm assures the coni, i tinuation and completeness of the chemical reaction. These previously known gas-producing materials ob- As an example the reaction" following equation (1) of Table I .was-conductedunder pressurized helium environment in a Crawford Bomb. The gas .analysis after completion of the chemical-reaction produced 67 mol percent oflnitrogen, 30 molpercent of Oxygen, and traces of water.

7 Under the conditions of this experiment the water to be produced in the reaction appeared in condensed form and only the amountof waterwapor.requiredfor the saturation of these gases was found in gas analysis. The residual composition was identified'to be sodium'chloride. The formation of the-reaction "gasestollowed essentially the Patented June 4, 1974v equation (1) of Table I. Only a minor amount of nitrous oxide was identified as a product of a minor side reaction probably formed during the ignition phase. Nitrous oxide is a non-toxic gas used for medicinal purposes. The reaction proceeded in a measurable form. Table III and Table IV hereinafter prove the composition of matter does not act as an exposure but as a mixture that produces the gases in a chemical reaction without explosive force.

This selection of reducing agents and oxidizing agents produces in their chemical reaction only such gases as contain no carbon, nor any toxic gases such as N or NO. The materials are mixed in proportions which form compositions which are preferably stoichiometric, although a degree of olT-stoichiometric mixing can be tolerated without incurring toxic gases. A material present in an oif-stoichiometric amount should not be olf-stoichiometric to an extent which changes the reaction mechanism and no longer insures safe gases.

Typical reducing agents suitable for use are sodium azide (NaN hydroxylamine hydrochloride (NH OHHCI) sodium nitride (Na N), silicon nitride (Si N sodium amide (NaNH magnesium nitride (Mg N sodium hyponitrite (Na N o hydrazine sulphate hydrazine hydrochloride (N H-2HCl), titanium hydride (Til-I zirconium hydride (ZrH magnesium hydride (Mg N- and calcium nitride (Ca N Typical oxidizers useful are ammonium perchlorate (NH ClO sodium perchlorate (NaClO potassium perchlorate (KClO sodium chlorate (NaClO potassium chlorate (KClO sodium nitrate (NaNO potassium nitrate (KNQ lithium nitrate (LiNO ammonium nitrate (NH NO barium nitrate (Ba(NO strontium nitrate (Sr(NO calcium nitrate M ah),

magnesium nitrate (Mg(NO zinc nitrate Sodium peroxide, barium peroxide, and potassium peroxide are capable of use either as a reducing agent or as an oxidizing agent depending on the particular selection of ingredients, and the same is true of sodium and potassium nitrite. Sodium azide, mentioned above as a reducing agent, can under certain exceptional circumstances be used as an oxidizing agent.

Typical reactions utilizing the foregoing identified materials are as shown in Table I below, and in these reaction equations, the respective reducing and oxidizing agents are indicated by the letters r and 0, respectively placed over the corresponding compound or compound groups.

TABLE I.REACTIONS 1. Na 13(0) NHcSlOKe) Na (c) 2Ni(g) 0.9 0 (s).

2. NeIGOfle) NH42110KC) Name) Nxg) 211.0 (Lg) m.

3. 2N:N0:(0) NzHriIzSOKc) V NM K lig) i .8)

s. billion-Home) Na lodc) Na01(c) N:(s) 1 20 (LE) M 205)- c. NHzO I KHCMc) N Notm) Nao1(c) 211:0 (Lg) de).

TABLE I-Continued asiom) 3NaC1(c) 4Ni(g) 1120 (Lu)- Nai IHflc) NHZCIOKQ) Name) me) 311.00 112m).

r o MgaN; NaClO; v NaCl 3Mg0 N1.

r o N830: 2NH4CIO 2NaCl N; 411 0 301.

r o NazN O 2NHC10| ZNaCl 2N, 30; 4Na0.

mmniso. Ba zNOzh 25 BaSO; 2N: 3Hz0 33/201.

NIHl-EHCI 2%IaNOi 2NaC1 2N: 311 0 3/20,.

Ti Ha E o T10; 2Hz0 K01.

The parenthetical letters (c), (g) and (I) placed adjacent to the compounds or products signify their condition as condensed, gas, and liquid, respectively. It

4 will be recognized that in these equations Ba may be replaced with Sr, Ca, Mg, or Zn; and Na may be replaced with K, Li, Rb or Cs.

Following are examples of reaction procedures which have been performed and their results.

EXAMPLE 1 A mixture of 65 parts ground sodium azide (particle size 10-100 micron)+117.5 parts ground ammonium perchlorate (particle size 5-250 micron) was pressed in a Carver press until almost theoretical density was reached. The resulting compression formed product may have the shape of a tablet, cylinder, cube or cone, depending on the selected mold. The density of the mixture was 1.781.785 g./cm. A reaction was conducted in the following manner: A Crawford Bomb was dried in a vacuum oven and a pellet weighing 1.7466 grams and measuring 0.377" thick, 0.386 wide, and 0.488" long 'of the above compressed stoichiometric mixture of sodium azide and ammonium perchlorate was placed inside the bomb. The system was purged and then pressurized with helium to 870 p.s.i. The volume of the bomb was approximately 20 infi. The pellet was ignited with a Nichromc wire. After a delay of about 0.26 seconds the pressure rose to 1458 p.s.i. in 0.27 seconds and then declined very slowly. Analysis of the gas exclusive of the helium showed:

Mole percent Nitrogen 67 xy 30.0 Nitrous oxide 1.7 7 Water 2.5 Ammonia 1 None 1 By IR and mass spectrograph.

The residue in the bomb had a pH of 7.0 and contained chloride. It is evident that the gas composition was close 3,814,694 5: '6 to that'expected from the theoretical stoichiometric reac- 4000 g'rams load and '3000.r'.p:m. In'the DTA anabrupt til15- fbm'l n m i l yg 111.3 2:1 molar ratio. exotherm with ignition occurred at 270 F. The density "J .1 a of the tablet was 2.0 gm./cm.

,1 As has been pointed out hereinabove, the chemical -tsg onn 5 1 m aZlde. 1 actions must produce a high exotherm so that the gas "Lmlcmn) and parts of ground 5 development is completed in a short time similar to'that of a combustion process. The exotherm calculations of .A dried m iirtur ticule size "105100. ammonium perchlorate, :(partic'le' size 5-250 micron) and 3.65ipartsofjromoxide.(particleisize 1-3 micron) was pressed using a rectangular mold until almost theoretical the senes of reactlons Show In Table I above are density was reachcdirhe vmsulfing compressed product sented in the following Table II wherein the equation was sawed into squares 0.33:1 X10386 x 0.488 in. Upon 10 numbers correspond with the same numbered equations initiation with: a Nichrome-wire in a Crawford Bomb in Table I.

TABLE IL-EXOTHERM CALCULATIONS AH keel. An (Gases) Mole weight H 1.) 11 0 (g.) Per mole Per 100 g. of com- [H2O (g.)/ [H20 (g.) position Mole Gram Mole Gram H20 (1.)] H20 (.1)]

"Kt'uhf'iiroddbts may e Bat) E 2 .1/2Q'2- f In theabove table, the expression "AH means drfierence of heat; the term keel means kiloealorles (eigher by under siimilar conditions but using nitrogen as gas, as The exothermcalculations in Table 11 show that the shown in Example 1, the materialedecomposed as shown reactions indeed produce heat. Considering equation 1,

in Table IV producing the theoretical"predicted'gases. for'example, it is seen that 182.512 grams, which is equal a .to 1 mole of the composition, produces 168.655 kilo- ECAMPLEQ 40 calories per mole, assuming that the water is produced as intimate dried stoichiometric mixture of tfinely va liquid. in the event the water he producedas'a gas, ground Sodium aZide, and finely QP ammonium P the same mole of the composition produces 147.601 kilochlorate, particle size of 5-19 micron nboth, waspressed calories .per mole. These .figures iurther show that for in a tablet press to form pills of /2 inch in diameter and every gram of the composition there is produced .924 B i ch i h t blets had adensity 0f 1- 3 g JOmkilocalories in the event the water is produced as a liquid,

Thesetabletswe Noweightf am a c orded afteiri" hon xposeewair'arroom temperatureand .808 kilocalories in the event the water is produced 0 ab orpt' or moisture was reas a gas. With regard to the number of moles of gas pro i t 'duced by equation l, 182.512 grams of the composition L produce 5 moles of gas in the case of the water being i produced as a gas, and only 3 moles of gas in the case An intimate e fi finely of water being produced as a liquid. Considering d l ammonium Perchlorate, Particle grams instead of 182.512 grams, the number of moles Size O 1 Produced in Example 3, produced at 2.739 for the water produced as a gas and was' safety'tested; The results an the blended powder show 1543 f r h water d d as a 1i id that material isflowpa'rficulaljy Sfinsitive impact, 5 The significance of the slanted lines between the numfl-ictionqr elevateidfempfaturveij bers of a pair is that the number of the pair at the left represents the gaseous phase and the number at the right Y r a s indicates the liquid phase. Referring again to the data for A saturated aquedu 'ssoiu tion ofsodium azi d a equation" 1,- the expression 5/3 means 5 in the case of saturatedaqueous -solu t'ion-of'arrimonium perchlorate in 09 s nd-'3 i 'the case of li uid; and 2.739/1.643 means STOiChiOi'lietfic ratibweftsPTytidifltd a Vacuum chamber 2;.739riioles of" and 1.643 moles Jwheu condensed; WhTeEY $O1V11tfWa$ p i y if p df 6 Thesefigures show-how an air bag collapses after it has ammonium perchlorate crystals were gasfpf dducing reaction according to fb'rmedin. v ry mart artid S -j "dried 1 01 6 equation II It: isdesired to create'a large number of moles was thencollected'andcompressedt the desired shape; ara "anti not'toomuch heat. 1 The density'of'tlie product was i Th timbers for f'thej' remaininge'quations in Table II haveinits eliemicai v 'duce'd' in {Ei'rarhpl srgniiicancesimilar to that'stated for the num 'bers'forequatior'i"1." A

The rapidity of the chemical reaction can be increased or influencedby the use of catalysts and catalysts may b'e sme re which promote ordecrease'the rate of the decompositionfof the oxidizer, chemi'eals used in the compo'sitionf-Typieal catalysts 'for'promoting the decomposi- 'tion' t"-ammoniurn perchlorate when it isused 'as an e ro'tary friction" st "at 7? oxidizer"ar"e iron oxides,chromium salts and the like.

' 7 Decomposition rates for typical equations are given in Table III as follows:

TABLE IIL-DECOMPOSITION RATES A pressure test in respect to equation 1 revealed results set forth in Table IV as follows:

TABLE IV.PRESSURE TESTS Pressure Pressure, increase, p.s.l.a.

p.s.i.a. Weight, Ob- Pre- Material grams 1st Peak Final served dicted NH4Cl04/NaNa 1. 569 2, 450 3, 215 2, 470 20 20 This test was performed in a 29.24 cubic inch bomb filled with nitrogen with initial (1st) and final temperatures at 73:0.5 F.

Besides the measurement of the actual rate of decomposition in the chemical reaction producing safe gases, other safety tests indicate the decomposition of matter is not hazardous. This is shown in the DTA (Difierential Thermal Analysis) data, the impact sensitivity data, and the friction sensitivity data of Table V below which indicates that the safe handling of this composition of matter is also proven.

perchlorate, sodium nitrite, sodium nitrate, sodium chlorate, bariumnitrate, potassium perchlorate, and at least one of which is a reducing agent selected from the group consisting of sodium azide, sodium nitrite, hydrazine sulphate, hydroxyzamine hydrochloride, sodium nitride, silicon nitride, sodium amide, magnesium nitride, sodium peroxide, sodium hyponitrite, potassium nitrite, titanium hydride, zirconium hydride, magnesium hydride, and calcium nitride.

2. A composition of matter which upon combustion yields non-toxic to human gaseousproducts, which composition consists essentially of a stoichiometrix mixture of an oxidizer compound ammonium perchlorate and a reducing agent selected from the group consisting of so dium azide, sodium nitrite, sodium nitride, silicon nitride, sodium amide, magnesium nitride, sodium peroxide, sodium hyponitrite, potassium nitrite, and calcium nitride.

3. A composition of matter which upon combustion yields non-toxic to humans gaseous products, which composition consists essentially of a stoichiometric mixture of an oxidizer compound sodium nitrite and a reducing agent selected from the group consisting of hydrazine sulfate and hydroxylamine hydrochloride.

4. A composition-of matter which upon combustion yields non-toxic to humans gaseous products, which composition consists essentially of a stoichiometric mixture of an oxidizer compound sodium nitrate and a reducing agent selected from the group consisting of hydrazine sulfate, and hydroxylamine hydrochloride.

5. A composition of matter which upon combustion yields non-toxic to humans gaseous products, which com- TABLE V. SUMMARY OF DATA ON GAS GENERANTS Safety tests DTA Impact sensitivity 1 Rotary friction I point), load, grams/ Temp. Material cm./2 kg. velocity, r.p.m. F. Observation 24 4000/6000 :1 3 Endotherm' C O NaN nega ve o. NH4 1 4/ 3 Exotigenm 0. Cl NaN 2 F60 10.5 4,000/3000negatlve 4,000/ 460 Endotherm. 04/ 2 a 7,000 positive. g2; Exogwrm.

1 RDX control 32. 1 Typical solid propellant control 2,080-2,200 gram load at 3,000 r.p.m.

It is understood that the oxidizing agents used in the 45 position consists essentially of a stoichiometric mixture reactions described herein may be mixtures of any two or more of the oxidizers, and likewise the reducing agents used in the reactions may be mixtures of any two or more of the reducers.

The compositions of matter described herein can be used in various applications. Besides the use as a gas augmentor producing non-toxic gases in air bag applications, there are other uses envisaged. For example, those compositions of matter which produce oxygen in the decomposition reaction would be suitable in devices for emergency oxygen generation. Such emergency oxygen generators are life savers in space applications, in mine disasters, in submarine applications, or any other application in which oxygen is being used to sustain life. The reaction temperature and the hot gases formed in the decomposition make these compositions of matter suitable in applications of solid rocket motors, as turbo starter initiators for jet engines, in gas generators where gases are needed on command, such as in steering of missiles, ships and other transportation vehicles. Rapid gas generation is also desired in application of emergency brakes and in military applications such as flares or incendiary devices.

We claim: a t

1. A carbon-free composition of matter capable of yielding gaseous products non-toxic to humans, upon combustion of the composition said composition consisting essentially of a stoichiometric mixture of at least two difierent compounds, at least one of which is an oxidizing agent selected from the group consisting of ammonium of an oxidizer compound sodium chlorate and a reducing agent selected from the group consisting of hydrazine sulphate, sodium amide, magnesium nitride, titanium hydride, zirconium hydride, magnesium hydride, and calcium nitride.

6. A composition of matter which upon combustion yields non-toxic to humans gaseous products, which composition consists essentially of a stoichiometric mixture of an oxidizer compound barium nitrate and a reducing agent selected from the group consisting of hydrazine sulphate, hydroxylamine hydrochloride, sodium amide, magnesium nitride, titanium hydride, zirconium hydride, magnesium hydride, and calcium nitride.

7. A composition of matter which upon combustion yields non-toxic to humans gaseous products, which composition consists essentially of a stoichiometric mixture of an oxidizer compound potassium perchlorate and a reducing agent selected from the group consisting of hydrazine sulphate, hydroxylamine hydrochloride, sodium amide, magnesium nitrid titanium hydride, zirconium hydride,.magnesium hydride, and calcium nitride.

8. A composition according to claim 1 in which the oxidizing agent is ammonium perchlorate and the reducing agent is sodium azide. l

9. .A composition according to claimv 1 in which the oxidizing agent is ammonium perchlorate and the reducing agent is sodium nitrite.

10. A composition according to claim 1 in which the reducing agent ishydrazine sulphate and the oxidizing agent is sodium nitrite.

11. A composition according to claim 1 in which the oxidizing agent is sodium nitrate and the reducing agent is hydrazine sulphate.

12. A composition according to claim 1 in which the reducing agent is hydroxylamine hydrochloride and the oxidizing agent is sodium nitrite.

13. A composition according to claim 1 in which the reducing agent is hydroxylamine hydrochloride and the oxidizing agent is sodium nitrate.

14. A composition according to claim 1 in which the reducing agent is sodium nitride and the oxidizing agent is ammonium perchlorate.

15. A composition according to claim 1 in which the reducing agent is silicon nitride plus sodium azide and the oxidizing agent is ammonium perchlorate.

16. A composition according to claim 1 in which the reducting agent is silicon nitride plus sodium nitride and the oxidizing agent is ammonium perchlorate.

17. A composition according to claim 1 in which the reducing agent is silicon nitride plus sodium amide and the oxidizing agent is ammonium perchlorate.

18. A composition according to claim 1 in which the reducing agent is sodium amide and the oxidizing agent is ammonium perchlorate.

19. A composition according to claim 1 in which the reducing agent is silicon nitride plus sodium nitride and agent is sodium chlorate.

20. A composition according to claim 1 in which the reducing agent is sodium peroxide and the oxidizing agent is ammonium perchlorate.

21. A composition according to claim 1 in which the reducing agent is sodium hyponitrite and the oxidizing agent is ammonium perchlorate.

22. A composition according to claim 1 in which the reducing agent is potassium nitrite and the oxidizing agent is ammonium perchlorate.

23. A composition according to claim 1 in which the reducing agent is hydrazine sulphate and the oxidizing agent is barium nitrate.

24. A composition according to claim 1 in which the reducing agent is hydrazine hydrochloride and the oxidizing agent is sodium nitrate.

25. A composition according to claim 1 in which the reducing agent is titanium hydride and the oxidizing agent is potassium perchlorate.

26. A composition according to claim 1 in which the reducing agent is zirconium hydride and the oxidizing agent is potassium perchlorate.

27. A composition according to claim 1 in which the reducing agent is magnesium hydride and the oxidizing agent is potassium perchlorate.

28. A composition according to claim 1 in which the reducing agent is calcium nitride and the oxidizing agent is potassium perchlorate.

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